Mechanically-worked zinc product



Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

wmms mirnmcn AND EDMUND A. ANDERSON, or PALMERTON, PENNSYLVANIA,

ASSIGNORS To THE NEW JERSEY zINc COMPANY, or NEW YORK, N. Y., A CORPO- RATION 01 N EW JERSEY.

MECHANICALLY-WORKED ZINC PRODUCT.

No Drawing.

This invention relates to mechanically worked zinc products, such as rolled sheet or strip zinc, and has for its object the provision, as a new article of manufacture, of an 5 im roved zinc product of this nature. In its roader aspect, the invention contemplates the provision of a new zinc base alloy particularly adapted for the fabrication of superior mechanically worked zinc products.

In the production of-rolled zinc, either by strip rolling or pack rolling, the properties of the finished rolled strips or sheets depend upon the composition of the zinc metal, as well as upon the rolling practice. Thus, a substantially pure zinc metal, such as the well known Hprsehead or other high grade brands, yields a very soft and ductile strip or sheet under suitable conditions of rolling. On the other hand, the more common grades of zinc metal, such as the well known Prime Western or other lower grade brands, which are natural alloys of zinc, lead and cadmium containing higher percentages of cadmium than present in high grade zinc metal, yield when rolled under appropriate conditions a stiffer and harder product than can be secured from a high grade zinc metal.

The stiffness of the strip or sheet rolled from the less pure grade of zinc gives for certain purposes distinct advantages over the softer product rolled from high grade zinc. For-example, one of the uses of rolled zinc is in the fabrication of corrugated sheets for roofing and siding purposes on buildings. Here stiffness is of great importance, since it determines the gauge of zinc necessary to give adequate strength and resistance to plastic deformation or flow when the sheets are laid on the building purlin's.

It is a recognized fact that zinc, like other metals of relatively low melting point, undertil goes slow plastic deformation or flow when subjected continuously to loads as low as a quarter of the ultimate tensile strength measured by ordinary tensile testing methods. For corrugated zinc sheets used as roofing, where the sheets must support snow loads and other loads continuously for considerable intervals, resistance to this plastic deformation or flow is one of the important properties.

Our investigations and experiments have indicated that the amountof stifl'ening and increased resistance to plastic deformation or flow which can be secured through solid solu- Application filed Februarz 9, 1928. Serial No. 258,213.

tion forming allo ing elements, such as cadmium, is limite and we have, therefore, experimented with alloying elements which introduce a separate hardening constituent 1nto the structure of the ultimate zinc base alloy.

As a result of our investigations we have found that if copper and magnesium are added to zinc in suitable proportions, the desired change in properties is secured to a very marked extent. This is presumably due to the formation of a finely divided hard inter-metallic compound. Copper alone, in the amounts which we prefer, to use, goes into solid solutionand produces relatively little change in the properties of the zinc. Magnesium alone produces a distinct hardening. The combination of copper and magnesium in suitable relative proportions, produces a distinctly higher resistance to plastic deformation or flow than is obtained in commercial zinc sheets rolled from the natural or usual zinc-cadmium-lead alloys.

We have found that the additions of cop per and magnesium may be made to either high grade zinc metal relatively free from lead and cadmium, or to lower grade zinc metal containing natural or usual amounts of cadmium and lead, with the production of improved zinc base alloys having the valuable properties for rolling or other mechanical Working. Copper and magnesium in suitable amounts produce a stiffening and hardening effect in all of the zinc base alloys to which we have added them regardless of the grade of zinc metal used as a base. Our investigations, however, indicate that best results can be obtained when high grade, or substantially pure, zinc is employed.

We have found that the improved properties characteristic of the invention, that is increased stiffness and hardness and increased resistance to lastic deformation or flow, can be secured y including in a zinc base alloy containing at least 92% of zinc, from 0.05 to 5% of copper and from .005 to 0.5% of magnesium, with not to exceed about 2% of such other metals as are naturallyor otherwise included in the alloy. Preferably, however, the improved alloy of the invention contains a base of substantially pure zinc,

ing 97 to 99% of zinc, about-1% of cpplper, and about 0.01% of magnesium. eremaximum stiflness and hardness is desired, we refer to use, in com ounding the alloy, h'gll grade or substantia ly pure zinc metal, together with copper and magnesium in amounts just indicated.

The alloys of the invention may be compounded in any approved manner. In fabricating the improved mechanically worked zinc productsof the invention, the alloy is cast into in ots of appropriate size'and subseuently su jected to the contem lated meo anical working. Where the a 0y isto be rolled, the ingot 1s first given an appropriate number of passes through suitable roughlng rolls, and may then be finished by strip rolling or pack rolling, as desired, in 00111111105101]. with such temperature treatment as may be considered advantageous.

The following tables illustrate the 1mproved properties of rolled sheet zinc made of the Z1118 base alloy of the invention:

Alloy. Pb Cd. Fe. Cu. Mg.

1. Common metal mix 0. 36 0. 10 0. 02 2. High grade metal 0.05 0. 003 0. 008 3. 0f invention 0. 75 0. 10 0. 02 i 0 0 01 4. 0! invention 0.05 0. 003 0.008 1.0 0. 01 5. 0f invention 0.05 0.003 0. 008 1.4 0. 007

Hardness D mic Ailo Gauge sclero- Temper y 30mm ductility Tensile strength. Elongation.

wgu mg stptic load a. sq. m. Alloy. in 2 in Time in hours to 5% With Across elongation at grain. grain.

With Across greln grain. O.

Strip too narrow for cross grain test.

' A study of these data will readily show the products made directly from either high or low grade zinc. Tests conducted at 20 C. (with static loads of 8000 lbs/sq. in.) for ex ample, indicate that in the case of common or .nesium and a amazes low grade zinc products (from alloy No.1) it took 58.3 hours to secure a 5% elongation of the test s cimen, whereas in the use of a product of t e invention made from the same low grade zinc base (alloy No. 3) it took 3,310 hours to secure the same elongation.

Muchhe same situation obtains in the case of specimensmade from high grade, or substantially ure, zinc. Whereas a 5% elongatipn was 0 tained in 4&6 hours with such a specimen (allo No. 2), it took 5,550 hours for the same elongation with a specimen of the invention alloyed with the same high grade zinc.

' Zinc base alloys containing aluminum tend to undergo intercrystallin oxidation. This is objectionable inalloys intended for rolling. For this reason the alloys of the invention are substantially free of aluminum.

The principles involved in the compounding of zinc base alloys capable of being mechanically worked into wrought products possessing superior resistance to cold flow are disclosed in our copending patent application, Serial No. 346.493, filed March 12., 1929. The resent invention is a species of that broad invention and is s ecifically directed to a zinc base alloy con orming to the principles underlying that broad invention.

We claim 1. As a new article of manufacture, a mechanically worked zinc product made of a zinc base alloy substantially free of aluminum and containing not less than 92% of zinc, from 0.005 to 0.5% of magnesium, and from 0.05 to 5% of copper.

2. As a new article of manufacture, a mechanically worked zinc product made of a zinc base alloy containing 0.0050.5% magnesium, and 0.055% co per, the remainder of the alloy consisting 0 high grade zinc metal.

3. As a new article of manufacture, a mechanically worked zinc product made of a zinc base alloy substantially free of aluminum and, containing not less than 95% of zinc, from 0.5 to 2% copper, and magnesium in amount not exceeding 0.5%.

4. As a new article of manufacture, a mechanically worked zinc product made of a zinc base alloy containing 0.52% copper and 0.005-0.1% magnesium, the remainder of the alloy consisting of high rade zinc metal.

5. As a new article 0 manufacture, a mechanically worked zinc product made of a zinc base alloy substantially free of aluminum and containin not less than 95% of zinc about 0.01% 0 magnesium, and about 1% of copper.

6. -As a new article of manufacture, a mechanically Worked zinc product made, of a zinc base alloy containing about 0.01% magout 1% cop er, the.remainder of table alloy consisting 0 high grade zinc met 7. A zinc base alloy substantially free of magnesium and 0.052% copper, the remainder of the alloy consisting of high grade zinc metal.

11. A zinc base alloy substantially free of aluminum and containing not less than 95% of zinc, about 0.01% of magnesium, and about 1% of copper.

In testlmony whereof we aflix our signatures.

WILLIS M. PEIRCE. EDMUND A. ANDERSON. 

